The present invention relates to an apparatus for accumulating or forming stacks of paper sheets or the like. More particularly, the invention relates to improvements in an apparatus for converting one or more reels or analogous sources of supply of flexible sheet, band or web material into stacks or piles containing preselected numbers of superimposed sheets, i.e., of sheets which overlap each other and can be used for the making of pads, books, pamphlets, brochures or the like. Such apparatus can be resorted to in connection with the mass production of the above-enumerated commodities, especially steno pads, exercise books, memo pads or like stationery products.
The trend in the paper processing industry and analogous industries is to accelerate the production of stationery products, books or the like. Certain presently known apparatus for the making of stacks of paper sheets or the like already employ several sources of supply of convoluted web, band or strip material and a cross cutter or an analogous severing device which simultaneously severs two or more webs so that the rate of making discrete sheets is multiplied, i.e., such rate equals the number of simultaneously severed webs multiplied by the frequency at which the severing apparatus cuts the webs so that each severing operation entails the making of a group of two or more overlapping or superimposed sheets. The groups are assembled into stacks wherein the total number of sheets is necessarily a whole multiple of the number of sheets in a group, i.e., if a group contains six sheets, the total number of sheets in a fully assembled stack must be a whole multiple of six. A drawback of such procedure is that the rate at which the cross cutter or an analogous device severs a plurality of webs to form a succession of groups cannot be increased at will because the removal of a fully assembled stack from the respective (stacking) station takes up a certain interval of time which, as a rule, is longer than the shortest interval between two consecutive severing operations if the cross cutter were permitted to operate at a reasonably high speed or at a maximum speed. In other words, it is not possible to increase the rate of making individual groups of sheets at the will of the attendants and/or at the will of the manufacturer because the removal of fully assembled stacks is the longest-lasting phase of the operation so that all other phases (which could be completed at a much faster rate) must be slowed down for the sole purpose of ensuring satisfactory removal of a fully assembled stack. Such removal not only involves physical transport of a fully assembled stack away from the stacking station but also the preparation of this station for reception of groups of sheets which are to form the next-following stack. Therefore, simultaneous conversion of two or more webs of paper or the like into discrete sheets and the gathering of such sheets into stacks cannot be performed at a speed which would be possible in view of the capacity of certain components (such as the cutoff) because the removal of stacks, especially of stacks which are assembled of groups containing relatively small numbers of sheets, is too time-consuming (as compared with the intervals of time required to carry out other operations, such as cross cutting) and necessitates a slowdown of the entire operation.
German Offenlegungsschrift No. 2,835,416 discloses an apparatus for transferring layers which consist of several sheets of paper or the like from a layer-forming or gathering station to a further processing station. The apparatus employs a tongs serving as a means for transferring layers from the gathering station to a removing conveyor which, in turn, transports the layers to the further processing station. Each layer is assembled of discrete sheets. The means for moving the tongs to and from its receiving position at the gathering station includes a drive which is independent of the main prime mover of the paper processing machine and includes a discrete prime mover as well as a mechanical transmission which is interposed between the discrete prime mover and the tongs. The mode of operation of the independent drive is such that the tongs must be accelerated from zero speed (position of dwell at the gathering station), that the tongs must be closed to engage a fully assembled layer of sheets at the gathering station, that the tongs extracts the engaged layer from the gathering station, that the tongs transfers the extracted layer to the removing conveyor (which delivers such layer to the further processing station), and that the tongs thereupon reassumes its idle position of dwell adjacent to the gathering station. The same sequence of steps is repeated when the next fully assembled layer is ready for transfer from the gathering station to the further processing station. Thus, the tongs is driven intermittently which is not conducive to rapid removal of layers from the gathering station. Moreover, the removing conveyor is not designed to deliver successive layers to a stacking station but rather directly to a further processing station, i.e., each layer can be said to constitute a small stack and the aforediscussed problems which arise when a stack is assembled of a series of groups of sheets (rather than from discrete sheets) remains unsolved. The only advantage of the procedure which is proposed in the German publication is that it renders it possible to assemble layers each of which contains a predetermined number of sheets, i.e., it is possible to count the individual sheets on their way to the gathering station and to remove a layer from such station when the counting operation indicates that the layer contains a desired (odd, even, large or small) number of superimposed sheets.